1. Field of the Invention
The present invention relates to a vehicular rear suspension system which includes a knuckle rotatably supporting a rear wheel via an axle, a trailing arm extending from a joint on a vehicle body in the longitudinal direction of the vehicle body and connected to the knuckle, and three lateral arms extending from joints on the vehicle body in the lateral direction of the vehicle body and connected to the knuckle.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 7-186649 discloses a multi-link suspension system which includes a trailing arm, a leading arm, an upper arm, a lower arm, and a control arm.
In the known multi-link suspension system, high caster rigidity and high longitudinal compliance are achieved by imparting a modulus of elasticity that is relatively high in the tensile direction and relatively low in the compressive direction to an elastic bushing. At least one of a connecting part between the leading arm and a knuckle and a connecting part between the leading arm and a vehicle body is provided with the elastic bushing.
In a suspension system equipped with three lateral arms, that is, an upper arm, a lower arm, and a control arm, the position of an elastic kingpin is determined based on the arrangement and the rigidity of each lateral arm in the lateral direction of a vehicle body. In particular, the rigidity of the lateral arms in the lateral direction of the vehicle body is determined based on the elastic coefficient of rubber bushing joints connecting opposite ends of the lateral arms to the vehicle body and a knuckle. However, where the elastic coefficient changes from a designed value, the position of the elastic kingpin is displaced from a designed position. Furthermore, when a lateral force acts from the road surface on a rear wheel during turning of the vehicle, rear wheel toe-out occurs, leading to a degradation in steering stability.